Two studies presented today (Tuesday 21 June 2005) at the 21st annual conference of the European Society of Human Reproduction and Embryology provide further proof that single embryo transfer (SET) produces babies that are healthier than those born after multiple implantations.

Dr. Diane De Neubourg, from the Centre for Reproductive Medicine, Antwerp, Belgium, told the conference that babies born after (SET) are as healthy as singleton babies born after a spontaneous conception. She said that these findings, from the first well-documented follow- up of SET outcomes, further underlined the principle that SET was good clinical practice in IVF and ICSI.

Dr. De Neubourg and her team began by studying the outcomes of all SET pregnancies originating from IVF and ICSI at the Centre for Reproductive Medicine. In addition to analysing existing data, they sent questionnaires to all patients after birth or termination with questions about the pregnancy, delivery, and outcome of the children. These data were compared with data on spontaneously conceived singleton children from the Flemish register of perinatal epidemiology, which collects information from all Flemish obstetric units.

During the period, the overall percentage of SET as opposed to multiple embryo transfers was 33.2 percent The percentage of SET increased from 12.4 percent in 1998 to 53.8 percent in 2003, and the proportion of singleton pregnancies from IVF/ICSI from 66 percent in 1998 to 87 percent in 2003.

"We analysed the outcomes of the 251 SET pregnancies and births and found very little difference between the SET babies and those conceived naturally", said Dr. De Neubourg. "Birth weight was very similar, and so was gestational age. Stillbirth was also the same in both groups. The only significant difference we found was that SET pregnancies reported more hypertension (7.6% as opposed to 4.6). "We began this study because we wanted to investigate whether babies born after SET would have similarly poor obstetric outcomes to those reported from singleton births at the time when it was customary to transfer two or more embryos. We believe that our work shows clearly that SET is best both for mother and child. But we need to gain more data over a longer period of time. We intend to make a sub-analysis for different groups of patients and to further elucidate aspects of infertility and implantation."

Health economic aspects of ART are becoming increasingly important, said Dr. De Neubourg. "It is clear that more singletons who are healthy will cost less to society. In Belgium this understanding has resulted in laboratory costs for IVF and ICSI being reimbursed under a strict embryo transfer policy to secure the prevention of multiple pregnancies."

In another presentation, Dr. Anja Pinborg, from the Fertility Clinic at the Rigshospitalet, University of Copenhagen, Denmark, told the conference that the major health risks for IVF singleton babies came from their being the surviving twin from a dual embryo transfer. She and her team studied data collected between 1995 and 2001 from 11 Danish fertility clinics to assess the number of born IVF singletons in which a spontaneous reduction ('vanishing twin') occurred during pregnancy.

The team looked at the obstetric and long term outcomes of these singletons, and examined whether a poorer outcome for the babies was linked to the gestational age at the time of the spontaneous reduction. "Of all the IVF singletons born", said Dr.Pinborg, "10.4% originated from a twin gestation in early pregnancy. We found a clear correlation between the incidence of neurological problems in these babies and the time of onset of spontaneous reduction ? the later in pregnancy the twin was lost the higher the risk of neurological problems in the survivor. Furthermore, the risk of child death within the period of follow-up was higher in the survivors of a vanishing twin than in those born from a single gestation."

Dr. Pinborg said that she considered that single embryo transfer (SET) should be recommended to women of less than 37 years of age with at least two high quality embryos available. "Perhaps the age criteria could be even higher ? that depends on future studies", she said. "We need to inform our patients that vanishing twins are a considerable risk factor in IVF twin pregnancies and a relatively common consequence of dual embryo transfer", she said.